PHILAE: Science scheduling and unknown context. leassons learned

Rosetta is an ambitious mission launched in March 2004 to study the nucleus as well as the coma of the comet 67P/Churyumov-Gerasimenko. It is composed of a space probe and the Philae Lander. The mission is a series of premieres: among others, first probe to escort a comet, first time a landing site is selected with a so short notice, first time a lander has landed on a comet nucleus. The space probe Rosetta reached the vicinity of the comet in spring 2014 when it has started to study Churyumov-Gerasimenko with remote sensing instruments. An intense observation phase followed to be able to select a landing site for the Lander. And in November 2014, at a distance of about 3 AU from the sun, Philae has reached its destination on the surface of the comet 67P. Once stabilized on the comet, the lander has performed its “First Science sequence”. Philae’s aim was to perform detailed and innovative in-situ experiments on the comet’s surface to characterize the nucleus by performing mechanical, chemical and physical investigations on the comet surface. The main contribution to the Rosetta lander by the French space agency (CNES) is the Science Operation and Navigation Centre (SONC) located in Toulouse. Among its tasks is the scheduling of the scientific activities of the 10 lander experiments and then to provide it to the Lander Control Centre (LCC) located in DLR Cologne. Nevertheless, the specific context of the Rosetta mission made this task even more complex if compared to usual spacecraft or landers: indeed the teams in charge of the Philae activity scheduling had to cope with huge constraints in term of energy, data management, asynchronous processes and co-activities or exclusions between instruments. In addition to these huge constraints it is important to note that the comet, its environment and the landing conditions remained unknown until the separation time and that the landing site was selected a short time before it had to take place and when the baseline operational sequence was already designed. This paper will explain the specific context of the Rosetta lander mission and all the constraints that the activity scheduling had to face to fulfil the scientific objectives specified for Philae. A specific tool was developed by CNES and used to design the complete sequence of activities on the comet with respect to all constraints. The baseline scenario designed this way will also be detailed to highlight the difficulties and challenges that the operational team had to face. A specific focus will be given on the landing site selection and the impacts on the scientific operations scheduling. Moreover the actual sequence performed on the comet will also be detailed and analysed to deduce the lessons that could be learned from such an unprecedented endeavour. Indeed as for every mission of exploration the flexibility concept was anticipated but had to face unexpected events

The Philae Lander: Science planning and operations

Rosetta is an ambitious mission launched in March 2004 to study comet 67P/Churyumov–Gerasimenko. It is composed of a space probe (Rosetta) and the Philae Lander. The mission is a series of premieres: among others, first probe to escort a comet, first time a landing site is selected with short turnaround time, first time a lander has landed on a comet nucleus. In November 2014, once stabilized on the comet, Philae has performed its “First Science Sequence”. Philae’s aim was to perform detailed and innovative in-situ experi- ments on the comet’s surface to characterize the nucleus by performing mechanical, chemical and physical investigations on the comet surface. The main contribution to the Rosetta lander by the French space agency (CNES) is the Science Operation and Navigation Center (SONC) located in Toulouse. Among its tasks is the scheduling of the scientific activities of the 10 lander experiments and then to provide it to the Lander Control Center (LCC) located in DLR Cologne. The teams in charge of the Philae activity scheduling had to cope with considerable constraints in term of energy, data management, asynchronous processes and co-activities or exclusions between instruments. Moreover the comet itself, its environment and the landing conditions remained unknown until separation time. The landing site was selected once the operational sequence was already designed. This paper will explain the specific context of the Rosetta lander mission and all the constraints that the lander activity scheduling had to face to fulfill the scientific objectives specified for Philae. A specific tool was developed by CNES and used to design the complete sequence of activities on the comet with respect to all constraints. The baseline scenario for the lander operation will also be detailed as well as the sequence performed on the comet to highlight the difficulties and challenges that the operational team faced

Isotope ratios of H, C, and O in CO2 and H2O of the Martian atmosphere

Stable isotope ratios of H, C, and O are powerful indicators of a wide variety of planetary geophysical processes, and for Mars they reveal the record of loss of its atmosphere and subsequent interactions with its surface such as carbonate formation. We report in situ measurements of the isotopic ratios of D/H and O-18/O-16 in water and C-13/C-12, O-18/O-16, O-17/O-16, and (CO)-C-13-O-18/(CO)-C-12-O-16 in carbon dioxide, made in the martian atmosphere at Gale Crater from the Curiosity rover using the Sample Analysis at Mars (SAM)'s tunable laser spectrometer (TLS). Comparison between our measurements in the modern atmosphere and those of martian meteorites such as ALH 84001 implies that the martian reservoirs of CO2 and H2O were largely established similar to 4 billion years ago, but that atmospheric loss or surface interaction may be still ongoing